Attitude Control of Space Launch Vehicles by Using Model Predictive Control

Abstract

The idea of the model predictive control (MPC) is applied to a space launch vehicle attitude control in order to deal with two major issues of this field: the uncertain and time-varying characteristic of the dynamics. The rocket's parameters such as the mass and the stiffness are constantly changing with time and have uncertainty because it is not possible to test a flight model. Additionally, this study is focused on attitude control of the launch vehicle during its ascent stage. At this stage, the environmental condition is also changing with time, and there is uncertainty in local wind and atmospheric conditions. The latest designs, including a combination of H_∞ control and gain scheduling control, have been successfully applied to real systems. The gain scheduling control approach divides the entire flight time into multiple blocks. This approach requires significant time and labor because each block must have its own controller design. To simplify this design procedure, the goal of the study is to design a robust control algorithm that can directly respond to the time-varying characteristics of the system. In this paper, two controllers are designed: one for the time-varying system and the other for the uncertain system. The one has been designed with adaptive model predictive control (AMPC). AMPC can predict future behavior of the system more precisely than conventional MPC. The other controller uses the idea of linear matrix inequality (LMI) for robust MPC (RMPC). Through simulations, it is shown that AMPC is able to deal with time variations in dynamics and RMPC has robust stability.